#include<stdio.h>
 
int find_single_dog(int* arr, int sz)
{
	int i = 0;
	int ret = 0;
	for (i = 0; i < sz; i++)
	{
		ret = ret^arr[i];
	}
	return ret;
}
 
int main()
{
	int arr[] = {1,2,3,4,5,1,2,3,4,6};
	int sz = sizeof(arr) / sizeof(arr[0]);
	int ans = find_single_dog(arr, sz);
	printf("%d\n", ans);
 
	return 0;
}
